Slat roofs having rotatable slats are usually used to cover an outdoor area, such as a terrace covering or veranda roof, etc. In addition to said slats, a slat roof of this type may also comprise one or more additional slats, such as for example a few fixedly arranged slats. Using such a rotatably arranged slat shaft, the slats are rotatable between an open position, in which an intermediate space extends between the slats, and a closed position, in which the slats together form a closed shelter. By rotating the slats between these positions, it is possible to regulate the incidence of light, radiant heat and ventilation into the space underneath the slats. By directing the slats, it is possible to protect against the sun and/or wind or, on the contrary, to let them in.
In addition, the slats may optionally be provided slideably in the slat roof, with, in that case, the slats being typically slideable between a position in which they are spread out over the slat roof and a position in which they are substantially arranged at one side of the slat roof.
A problem with such slat roofs is that the beams begin to bulge (and bend outwards) under the weight and the bending of the slats suspended between them in the plane of these slats. Wind loads can also cause this phenomenon. On the one hand, this problem is becoming more widespread due to the growing trend of designing larger uninterrupted covers to have such slat roofs and of using heavier slats in such covers, such as glass slats, for example. On the other hand, this problem is also becoming more widespread due to another trend, namely to make these slat roofs simpler, so that they can also be installed by DIY enthusiasts.
In order to remedy this problem, the beams are often designed to be sturdier. However, this requires more material and means that the beams become a great deal more expensive, which also results in a considerable increase in the cost of the entire slat roof. Wider and heavier beams are often also undesirable for aesthetic reasons.
Beams may be placed at an incline (concave), counter to the bulging, so that they return to being straight as a result of the bulging. However, it is difficult to connect such beams neatly to other girders which in this case together form a frame for the slat roof. Such beams are difficult to mitre in an aesthetic manner.
A transverse girder may be provided in the centre of such a slat roof. However, most customers do not wish for such a division of their slat roof using such a transverse girder.
Recently, the present applicant devised a further solution using a tension cable which is fitted inside a hollow slat shaft. This solution was proposed in patent application BE 2015/5333. However, this solution using a tension cable in a hollow slat shaft cannot be applied to all slat roofs equally well. This solution is less suitable, for example, for relatively simple slat roofs where the beams are made in a single piece and, as a consequence, the ends of these tension cables cannot so easily be concealed in said beams.
Another possibility is to fit a circlip to the end of the slat shaft which is fitted through the beam and extends on the other side of the beam from that of the slat. However, this end is usually no longer accessible after the slat has been installed.